$\cos(\frac{2}{3}\pi) = \text{?}$
Solution: To find the cosine using the unit circle, first find the angle. Drag the orange point around the circle until $\frac{2}{3}\pi$ is selected. The correct angle is selected. Remember, the cosine of an angle is represented by the $x$ coordinate of a point on the unit circle. The $x$ coordinate of the point is $-0.5$, so $\cos(\frac{2}{3}\pi) = -0.5$.